The corpus callosum is a dense fibrous bridge that connects the two hemispheres in the brain. Originally its purpose was not understood. One scientist remarked in the first half of the twentieth century that it might just be there to keep the two hemispheres from falling in on each other. Sperry clearly did not take this view, and the function of the “bridge” began to fascinate him.
In 1940 researchers first noticed the spread of epileptic (electrical) discharge, the cause of epileptic fits, from one brain hemisphere to the other in monkeys; they believed this occurred through the corpus callosum (Gazzangia, 2005). It was in this same year that William van Wagenen and R. Herren performed the first corpus callosotomies – essentially, the bisection of the brain into two separate hemispheres – to prevent epileptic fits in human patients (Matthews et al, 2008). By severing the corpus callosum, the epileptic discharges could not cross to the other hemisphere, thus preventing seizures the human patients had been suffering from. It appeared an operable cure for severe epilepsy had been found.
In 1944 A. J. Akelaitis began to study the first human split-brain patients to see if “there were any cognitive or behavioural effects as a result of the surgery” (Gazzangia, 2005). It became apparent very quickly that there were no disruptions of general intellect, nor was there impact on personality or temperament as a result of the procedure (Sperry, 1966b).
About ten years later, Sperry and his colleagues began to research split-brain rats, cats and monkeys; these early animal studies helped develop a set of more “sophisticated techniques to directly assess the function of each hemisphere independently” (ibid).
The ability to assess each hemisphere separately showed that the distinct sections of the brain solved problems differently. At the August 1968 meeting of the National Academy of Sciences, Jerry Levy-Agresti and Sperry presented that
the mute, minor hemisphere is specialised for Gestalt perception, being primarily synthesist in dealing with information input. The speaking, major hemisphere, in contrast, seems to operate in a more logical, analytic computer-like function. Its language is inadequate for the rapid complex syntheses achieved by the minor hemisphere. (Levy-Agresti & Sperry, 1968)It was beginning to appear as if there were two minds within a single brain, theoretically meaning everyone had two consciousnesses.
In one experiment with a split-brain patient, a pornographic image was shown to the patient’s left eye. The left side of their face began to blush. When asked why they were blushing they didn’t know, they didn’t know they were looking at anything. This is because the left eye crosses to be connected with the right hand side of the brain. Language comes from the left side of the brain; this means when the patient is asked what they are looking at their brain doesn’t know the right hand side, their left eye, is looking at anything, as the connection between the two had been severed. This experiment showed that the two hemispheres are separately conscious at the same time. Sperry later wrote that
both the left and the right hemispheres may be conscious simultaneously in different, even in mutually conflicting, mental experiences that run along in parallel.It appeared as if consciousness could no longer be perceived as a single entity; it still remained, however,
a will-o’-the-wisp, something [science] cannot find, cannot demonstrate, measure or work with, and in most cases, something just the general nature of which it cannot even satisfactorily conceive or imagine. (ibid)Consciousness was still “one of the most mysterious phenomena left in the whole of science” (ibid).
Following the “boom” period of split-brain research in the nineteen-sixties, more emphasis has been placed on the idea of two minds within each of us. Fredric Schifer’s book Of Two Minds argues that not only do we have two minds, but they also have their own distinct personality, making us two people in one body. To prove we have two minds that can work separately, Schiffer cites the case of a female split-brain patient. He writes:
A split brain patient was awakened by a hand slapping her across her face. Her alarm clock was going off, and she realised she had overslept and was going to be late for an appointment. The hand that had aroused her was her own left hand! While her left brain was asleep, he right brain [which controls the left hand] awoke and appreciated the predicament. (Schiffer, 1998)This supports Sperry’s call that both hemispheres can operate independently and can be mutually conflicting in their processes.
We still cannot physically locate consciousness, nor can we measure it or recreate it artificially. The split-brain research, which widened the view of consciousness, shows that we, as yet, cannot define the parameters of it.
John Locke was the first to define consciousness in 1690; he said it was “the perception of what passes in a man’s own mind” (Locke, 1690). But the more science looks into the construction of the brain, the assumed location of the mind and consciousness, we have to wonder what the extent of the mind and consciousness is, something which may expand beyond what we can perceive to exist.
Sperry and his work with split-brain patients, while never answering the question he first asked himself at university in the early nineteen-thirties, has instead left us with more questions: “How far does the process of our consciousness proceed?”, “Are we more conscious than we can consciously be aware of?”, “Do we indeed possess two conscious and separate minds in the one brain?” and “Do we really consciously know who we are as individuals if we cannot know the extent of our consciousness?”
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